Taurine is an essential amino acid for cats, and if not supplied in the diet, they become taurine depleted and suffer retinal and tapetum degeneration. Nursing cats supply the kittens with all of their nutrition, including taurine, which comprises the major portion of the free amino acid pool of cat's milk, presumably to supply this great need during development. We propose to examine the additional nutritional stress of pregnancy and lactation on cats receiving no dietary taurine. We will examine both the queen and the kittens, and their nutrition link, the milk, throughout the period of weaning. A nursing cat transfers the major portion of its body taurine to the kittens via the milk from birth to weaning, and since the cat has only a small capacity for biosynthesizing taurine, nutritional taurine takes on additional importance. Preliminary experiments suggest that dietary depletion of taurine during pregnancy results in resorbtions, abortions, stillbirths, and live, underweight kittens. Such kittens have a number of neurological defects. All queens and kittens will be examined for the following: reduced growth, changes in taurine concentration in plasma, in tissues, and in the milk, whether lactation continues normally, any obvious behavioral or clinical signs, and any defects in the retinas ophthalmoscopically, in electroretinograms, in visual evoked potentials, and ultrastructurally. These observations will be made when the diet is initiated after various lengths of gestation, and prior to conception. Prenatal and postnatal effects will be differentiated by cross-fostering, and by oral taurine supplementation. Experiments with graded levels of taurine in the diet will provide the minimum taurine requirement for normal pregnancy and for normal postnatal development. The degree to which cystine supplements can spare dietary taurine will be determined. The effects of nutritional taurine inadequacy during pregnancy and lactation should be greatest in the cat because of its rapid growth and greater dependence on taurine. However, human and non-human primate infants become taurine-depleted and suffer from some retinal problems and growth depression under taurine-free nutrition, since they also derive all of their taurine from the milk and have an even smaller capacity for taurine biosynthesis than the cat. The results from the proposed study will be useful predictor of the importance of dietary taurine to pregnancy and nursing in these species.